Text.Pandoc.UTF8: Use strict bytestrings in reading.

The use of lazy bytestrings seemed to cause problems using
pandoc on Windows 7/8 64-bit machines.

Closes #874.

src/Text/Pandoc/UTF8.hs

@@ -85,7 +85,7 @@ hPutStrLn :: Handle -> String -> IO ()
 hPutStrLn h s = hSetEncoding h utf8 >> IO.hPutStrLn h s
 
 hGetContents :: Handle -> IO String
-hGetContents = fmap toStringLazy . BL.hGetContents
+hGetContents = fmap toString . B.hGetContents
 -- hGetContents h = hSetEncoding h utf8_bom
 --                   >> hSetNewlineMode h universalNewlineMode
 --                   >> IO.hGetContents h